Plastic bag manufacture



United States Patent 72] Inventor Lawrence Salvatore Maccherone Emerson,New Jersey [21 1 Appl. No. 750,962

[22] Filed Aug. 7, 1968 [45] Patented Oct. 20, 1970 [73] AssigneeAmerican Can Company New York, New York a corporation of New Jersey [54]PLASTIC BAG MANUFACTURE 10 Claims, 4 Drawing Figs.

[52] US. Cl 93/35, 93/8, 156/344 [51] Int. Cl B3lb 49/04 [50] FieldofSearch 93/350213), 8; l5 6/344:53/(lr 1quired) [56] References CitedUNITED STATES PATENTS 3,395,622 8/1968 Kugler 93/35 PrimaryExaminer-Bernard Stickney Attorneys-Kenneth H. Murray, George P.Ziehmer, Robert P. Auber and Louis F. Heeb ABSTRACT: There is describeda method of and apparatus for making plastic bags having pleated bottomends capable of squaring up when the bags are filled, wherein novel waysand means are provided in association with the forming and sealing ofthe bottom pleats to separate the individual folds.

Patented Oct. 20, 1970 3,534,666

In S INVENTOR.

4 A WRENCE 5/11 m 7025 MArcllfmvf Patented Oct. 20, 1970 Sheet 2 of 2PLASTIC BAG MANUFACTURE BACKGROUND OF THE INVENTION This invention is animprovement in the art of manufacture of pleated or gusset bottomplastic bags. Flat formed plastic bags provide a relatively inexpensivepackage form and are used for a wide variety of merchandise. The gussetbottom construction, usually with an interconnecting triangularformation at each end of the W-shaped pleats, is becoming increasinglypopular because it enables the bag when filled to assume a squared offconfiguration at its bottom end, thereby providing a package of pleasingappearance and one which enables end stacking in situations where thisfeature is desirable. Examples of square bottom bags are described inUS. Pat. Nos 2,771,010; 2,815,063; 2,821,337; 3,023,679; and 3,136,475.

The particular construction of square bottom bags for which the presentinvention is intended is the type wherein the triangular formations atthe ends of the gusset result from the pleats being cut through and heatsealed along converging lines extending from the side seams which definethe width of the bag. In the manufacturing sequence contemplated, thetapered ends of the contiguous pleats are cut through and heat sealed atthe same time by a cutting-sealing tool. This operation has thedisadvantage of causing a degree of sticking or fusing between thegusset end seals, which makes it difficult for the bag to properlyassume its expanded, squared bottom configuration when filled withproduct. It is this problem which the present invention aims toovercome.

SUMMARY OF THE INVENTION The invention comprises a mechanism and theoperative steps for breaking apart or separating the pleats in thegusset fold of an article of manufacture produced from longitudinallyfolded heat scalable web. In the contemplated environment of use, thegusset pleats are cut and heat sealed at spaced increments along linesextending across the pleats at an angle to the path of feed of the web.The pleat seals are formed by means of a heat sealing tool which cutsthrough and seals the ends of the adjacent pleats in one pass. Thisoperation tends to cause local points of sticking or fusing between theseals of the adjacent pleats, which makes it difficult for the pleats toopen and expand properly in their intended function. By this invention,these points of fusion between the pleat seals are physically brokenapart by means of an elongate separator member which includes a thinfilament or wire positioned at its upstream end to lie between thepleats adjacent the fold line connecting the pleats and at itsdownstream end to a connection to the outside of the pleats. The pleatheat seals are formed at a station near the upstream end of the filamentand extend outwardly from the filament to the free edge of the pleats.When the heat sealed pleats pass over the downstream end of thefilament, any points of fusion between the pleats are broken.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic perspective view ofa bag making system utilizing the invention;

FIG. 2 is an enlarged diagrammatic plan view of a portion of the systemof FIG. 1. illustrating the novel means and its function in the practiceofthis invention; and

FIGS. 3 and 4 are perspective bottom end views of a bag formed by thepractice of this invention, before and after the bag is expanded byfilling with a pi oduct.

DESCRIPTION OF A PREFERRED EMBODIMENT The bag making systemdiagrammatically illustrated in FIG. I comprises a conventional folderguide which receives a web W of plastic sheet from a supply reel (notshown) over a guide roll 11, and a pair of driven pull rolls 12,12 whichpull the web W over the folder guide 10 and advance it toward a seriesof work stations.

As it is drawn off the guide 10, the web W is folded along alongitudinal line L intermediate its edges, thus bringing the adjacenthalves of the web into fiat superimposed relation as they pass throughrolls, 12,12 toward the other work stations. Immediately downstream ofthe pull rolls is a device, in the form ofa pleating disc 13 rotatablein the plane of the moving web, which engages the web along the foldline L and reversely tucks the marginal portions on each side of foldline I. in between the flat halves of the web, thus forming a W-shapedfold having two adjacent pleats, designated P and P (See FIG. 2).

The folded and pleated web next moves past a station where the foldedpleats l and I: are incrementally subjected to a cutting-and-sealingoperation. At this station, a triangularly shaped cutting-sealing tool15 reciprocates to and from engagement with the pleats to form thereinat spaced intervals, triangular V-shaped cutouts V which aresimultaneously sealed along the cut lines.

The triangular cutting tool 15, illustrated in FIG. I as a verticallyreciprocatable member having an electrically heated cutting and sealingblade 16 at its lower end, engages the folded pleats P and P,: at spacedintervals against a backing plate 17, whereby a triangular wedge T iscut from the pleats and the superimposed legs of each pleat are sealedalong the triangular cut lines. The backing plate 17 is provided with atriangular space 18 underlying the triangular tool 15, whereby thesevered wedges T are allowed to fall free as the cut-seal is made. Thebacking plate 17 is appropriately mounted for longitudinal and lateraladjustment on a frame section 19 which forms a part ofthe machine frame.

As the pleated web advances beyond the aforementioned cutting-sealingstation, the cut-and-sealed pleats pass over an elongate cooling device20 through which a suitable refrigerant is circulated. The cooling plate20 is bracketed to frame section 19. The V-shaped heat-seals are thuscooled to a permanent set.

The folded web with the now cooled Vshaped gusset seals next passesthrough the nip of a second pair of feed rolls 21,21, and then beneathan elongate cutting-sealing shoe 22 which extends transversely of thefolded web. Elongate shoe 22, also electrically energized and having anarrow elongate cutting-sealing edge 23, reciprocates to and fromengagement with the folded web to cut the web and form spaced transverseseals S extending across the folded web from the apex of the triangularseals V at intervals corresponding to the desired width of the bag beingformed. A conventional backing member, not shown, underlies the webbeneath elongate cutting-sealing shoe 22, and the finished bag B isdetached from the web at the seal line S by conventional off-feed belts,also not shown, which move at a faster linear speed than that of web W,thus facilitating the detachment of the finished bag from the side sealof the next succeeding bag.

From the preceding description, it will occur to the reader that the twopleats P, and P, are likely to be fused together at their edges as aconsequence of the cutting and sealing operation performed by triangularblade 16. A novel means is provided for solving this problem, as willnow be described.

Mounted on frame section 19 and extending between a point just beforethe location of cutting-sealing tool 15 to a point just before thelocation of feed rolls 21,21 is an elongate seal breaker, generallydesignated 30. As best illustrated in FIG. 2, the seal breaker comprisesa thin, elongate filament 31, preferable of durable material such aspiano wire. connected at each end and stretched between a spaced pair ofthin plates 32 and 33 which bolt to frame section 19 at theaforementioned locations. Plate 32 includes a bracket portion 32a withbolt slots for adjustable mounting to frame section 19, and acrescent-shaped blade portion 32b which projects into the folded gussetbetween pleats I and P and curves in the downstream direction towardplate 17. Similarly, plate 33 includes bracket portion 330 and bladeportion 33b which curves upstream toward plate 17 between the gussetpleats. The two plates preferably are constructed from sheet metal,

and the blade portions 32b and 33!) are quite thin, having a thicknesssubstantially equal to the diameter of wire 31. The upstream end of wire31 is secured to the leading edge of blade 32b, and the other end to thetrailing edge of blade 3312, with permanent connections, as, forexample, soldering.

It will be observed on examination of P16. 2 that the apex of theV-shaped blade 16 falls close to but just outside (transversely of thepath of vveb W) of wire 31 at this location. Consequently, thetriangular cut and seal V terminates to the outside of the wire, whichmeans that wire 31 is trapped" between the pleats P and P when the sealis made, in a nar row channel between the apex of the seal and fold lineL.

As the web is advanced downstream toward the next work station, the twopleats P, and P pass over the downstream end of wire 31 and blade 33b towhich it is secured, thus breaking apart any points of fusion betweenthe pleats that may have occurred during the formation of seal V. Thiscompletely separates the pleats from each other so that they remainfree, as illustrated in FIG. 3, and capable of ready expansion into thesquared-up configuration shown in FIG. 4 when the bag is filled.

The narrow channel in which wire 31 moves is subsequently sealed overand cut through by transverse shoe 22 in the formation of the side sealS. This produces an uninterrupted seal extending across the tapered endsof the pleats P, and P and up the opposite sides of the bag B, as bestshown in FIG. 4.

The above described structure of the seal breaker 30 and its mounting toframe section 19 is a preferred embodiment, but it is contemplated thatvariations of the principle will readily occur to those skilled in theart. For example, the downstream end of wire 31 may be differentlysupported and still achieve the pleat separating function, so long as itis held sufficiently taut to break through the points of fusion betweenthe two pleats as they move along.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the form, construction, andarrangement of parts of the apparatus mentioned herein and in the stepsand their order of accomplishment of the method described herein,without departing from the spirit and scope of the invention orsacrificing all of its material advantages, the apparatus and methodhereinbefore described being merely a preferred embodiment thereof.

[Claim 1. in a method of producing an article of manufacture from a webof heat scalable material wherein the web is longitudinally folded witha gusset of multiple pleats and heat seals are formed in the pleats atspaced intervals along the fold, the improvement comprising the stepsof:

a. passing the folded pleats over a thin elongate filament fixed at itsupstream end to lie between and adjacent the line of fold connecting thepleats and fixed at its downstream end to a connection to the outside ofsaid pleats;

b. forming at an upstream position along said filament a heat seal insaid pleats extending outwardly from said filament at an angle to thepath of web travel to fuse together the respective legs of the foldedpleats; and

c. advancing said heat sealed pleats over the downstream end of saidfilament to break apart any points of fusion occurring between saidpleats during the forming of said heat seal.

2. The method of claim 1 wherein said heat seal is formed in each ofsaid pleats at once.

3. The method of claim 1 wherein said heat seal is V- shaped, the apexof which is adjacent said line of fold.

4. The method of claim 1 and including the step of forming beyond thedownstream end of said filament another heat seal extending transverselyof said folded web from the first said heat seal in said pleats.

5. A method of forming flat gusset bottom bags from a web of heatscalable material, comprising the steps of:

a. longitudinally folding said web and forming at the line of fold agusset of multiple pleats;

b. inserting between the adjacent one of said pleats an elongate memberfixed at its upstream end to lie adjacent the line of fold connectingsaid adjacent pleats and fixed at its downstream end to a connectionlying outside the free edge of said pleats;

c. forming at spaced intervals along said gusset heat seals extendingfrom said filament across said pleats at an angle to the path of feed ofsaid web;

d. passing said heat seals over the downstream end of said elongatemember to break apart any points of fusion between said adjacent pleatsoccurring during the forming of said seals; and

e. forming transverse heat seals across said fold web from said heatseals in said pleats and separating the resulting bag from the web atsaid transverse heat seal.

6. In an apparatus for fabricating from heat scalable web an article ofmanufacture having a gusset of multiple pleats along a longitudinal lineof fold and heat seals across the pleats at an angle to the line of foldat spaced intervals thereon, the improvcment comprising:

a. a heat sealing tool operable at a station along said line of fold andpositioned to form said heat seals extending across said pleats from thefree edge thereof to adjacent the line of fold connecting said pleats;and

b. an elongate separator means extending both directions from saidstation for breaking apart any points of fusion between said pleatsoccurring during the forming of said seals, said means including a thinfilament positioned at its upstream end to lie between said pleatsadjacent their connecting line of fold and fixed at its downstream endto a connection lying outside of the free edge of said pleats, saidfilament at said station being positioned with respect to said tool tolie between said connecting line of fold and the inner terminus of saidheat seals.

7. The apparatus of claim 6 wherein said tool is operable to form saidseals in the adjacent pleats of said gusset in one pass.

8. The apparatus of claim 6 wherein said tool forms said seals in aV-shape, the apex of which is adjacent said connecting line of fold.

9. The apparatus of claim 6 wherein said elongate separator meansincludes blade-shaped members secured to the opposite ends of saidfilament and extending between said pleats of said gusset.

10. An apparatus for forming flat gusset bottom bags from a web of heatscalable material, comprising:

a. means for longitudinally folding said web to bring its halves intoclose superimposed relation and forming a gusset of multiple pleats atthe line of fold;

b. heat seal means for forming heat seals in said pleats extending at anangle to the path of feed from the free edge of said pleats to adjacentthe fold line connecting said pleats;

c. means for breaking apart any points of fusion occurring between saidpleats during the forming of said seals, said means including a thinelongate filament fixed at its upstream end to lie between said pleatsadjacent said connecting line of fold and fixed at its downstream end toa connection outside the free edge of said pleats; and

d. heat seal means positioned downstream of said filament for formingtransverse seals extending across said folded web from the innerterminus of said pleat seals.

